A commonly assigned U.S. Pat. No. 4,356,317 of Coleman, Hallcher and McMackins, issued Oct. 26, 1982 describes a procedure to react butadiene and acetic acid with metal ion oxidant to prepare acetoxyhexenoic acids. Commonly assigned U.S. Pat. No. 4,380,650 of Coleman, Hallcher and McMackins, issued Apr. 19, 1983, describes a procedure for converting acetoxyhexenoic acids to .gamma.-vinyl-.gamma.-butyrolactone. A. U.S. Pat. No. 4,175,089 describes a procedure for reacting olefins and acetic acid with metal ion oxidant to produce lactones. The prior procedures are generally conducted in solvents, e.g., in acetic acid, and separation of the product generally involves extraction procedures utilizing two immiscible solvents, such as diethyl ether and water. Particular separation procedures for .gamma.-butyrolactones are described in U.S. Pat. No. 3,992,417. Such procedures may employ a solvent for the lactone along with a non-solvent for the lactone which is, however, a solvent for the salts formed from the metal ion oxidant. The solvent for the metal salts then is removed prior to return of regenerated metal ion oxidant to the reaction zone. Similarly, removal of the lactone solvent from product will be necessary, and its removal may also be required before recycle of unreacted olefin. When water is the solvent for metal salts, considerable care in its removal is required to avoid contamination of the reaction medium.
The commonly assigned U.S. Pat. No. 4,356,317 referenced above is primarily concerned with production of acetoxyhexenoic acids rather than lactones. It happens that reaction rates and other factors are better under conditions producing acetoxyhexenoic acids. However, it has been found that .gamma.-vinyl-.gamma.-butyrolactone is more stable under preparation and distillation conditions than 6-acetoxy-4-hexenoic acid and 4-acetoxy-5-hexenoic acid, and therefore is a better compound for isolation purposes. Procedures for preparing acetoxyhexenoic acids and converting the acids to .gamma.-vinyl-.gamma.-butyrolactone are described and claimed in a simultaneously filed, commonly assigned copending application of Coleman et al, Ser. No. 503,979, now U.S. Pat. No. 4,526,990. The procedures of that application can be employed in the present invention to provide lactone-containing reaction mixtures for product separation.